Air Pump

I am looking at purchasing an air pump to aerate my wort. I have the tubing and air stone. Does anyone have any suggestions on the pump size. They have them at Petsmart for 20 gal and 40 gal tanks (or larger). Thanks.

I don't have a direct answer to your question, but we use the el-cheapo aquarium pumps from Walmart and they've worked great. I would bet they were for 20 gallon tanks since they're pretty small (about the size of a beer can). Keep in mind that the limiting factor on your flow rate will likely be the tubing and air stone. So, buying the larger air pump may not result in any more flow.

Another point to consider is whether there is a filter on the inlet to the air pump. On ours it looks like a thick wad of white cotton stuffed into the suction.

I am using a pump that was bought at Walmart intended to inflate inflatable beds.
I then pump air into the hose of a racking cane (sanitized) without air stone and just bubble the heck out of that beer before I pitch yeast.

I have seen people that put alcohol on air inlet filters so that they that way would sanitize the air. However I doubt how much effect that would have (would be fund to do a trial with blowing air to a petri dish to see if there was any significant changes depending on alcohol or no alcohol).